Text composing and formatting has followed a change from fully manual typesetting and editing, to automatic galley (column) formatters, thence to full page composers and formatters. Many text composers are interactive, that is, an operator makes most or all of decisions with the machine carrying out the decisions in an automated manner. Other composers and formatters were programmed on large-capacity digital computers to automatically perform the functions often performed by the operator in an interactive system. Such composers and formatters have been termed "host formatters". Such host formatters respond to embedded composing and formatting commands for converting unformatted text data streams into formatted text data streams usable by document presentation devices, such as printers of all types, terminals, microfiche and other types of information conveying apparatus.
An example of a host galley formatter is the PRINTEXT/370 program available from International Business Machines Corporation, Armonk, N.Y., as program RPQ EF3414, program number 5799-ALR and described in the Program Reference Manual number SH20-1794, 1976. A host page composer has many more functions than a galley formatter. These additional functions result in a more complicated program design. An example of such a page composer is found in the Licensed Program 5748-XX9, Document Composition Facility (DCF), of International Business Machines Corporation (IBM), Armonk, N.Y., and as described in publication numbered GH20-9158 (1978), among others. This program uses embedded commands which are definable using a Generalized Markup Language (GML) as described by W. B. Adams at the International Technical Communications Conference, May 1981, of the Society of Technical Communications, and held at Pittsburgh, Pa. The presentation was published as an article "Playing Tag with Automated Text Processing" in the proceedings of the Society. A more detailed description of GML is found in publications available from IBM identified as SH20-0188, "Document Composition Facility, Generalized Markup Language: Concepts and Design Guide" and SH20-9186, "Document Composition Facility--Introduction to the Generalized Markup Language: Using the Starter Set".
The DCF program enables a computer, or host processor, to format text into "logical pages" which define an area which receives formatted text for presentation on a sheet of paper (form) using a predetermined orientation, size and placement. A plurality of logical pages can be assigned to and printed on one form. DCF also divides each logical page into a plurality of mutually exclusive text and graphics receiving areas, portions, or regions. These areas extend the entire width of the printable portion of each logical page, hence are considered as vertical portions or segments. The order of such vertical segments on each logical page is fixed. Beginning at the top of a logical page, one first encounters a header space, then a title space, a running header, a body portion which is further divided into a plurality of vertical sections, a footnote space, running footer, a title and a footer. Surrounding the vertical spaces is a margin (a nonprintable portion along each edge of a logical page). None of these areas can overlap. Each of the sections in a body can be divided into vertical columns which are fully contained within each such section. This logical page format can extend throughout a document or a portion of a document. Automatic means are provided to change the vertical extents of these areas from one logical page to the next.
When DCF is being executed by a digital computer or host processor, the host processor when combined with a terminal, external data storage and a text output device becomes a highly automated text/graphics composer. While the facilities provided in such highly automated composition provide computer-aided assistance to users, yet more flexible automatic composition is needed for further enabling users greater flexibility and ease in composing and formatting documents and other information-presenting vehicles.